1. Field of the Invention
The present invention relates to a hybrid electric power device for a crane and a control method of the hybrid electric power device for the crane. Some cranes such as a gantry crane and a jib crane mounted with tires driven by an engine generator are driven by a mechanism of running a motor or the like using the engine generator and a hybrid electric power source including an electric power accumulating unit such as a battery.
The present invention relates to a hybrid electric power device for a crane used in a facility such as the gantry crane and a control method of the hybrid electric power device for the crane.
2. Description of the Related Art
As an example, an engine generator including a diesel engine or the like has been used to drive an electric motor in a crane or the like and an electric motor for driving a pump. In this crane or the like, an electric power generated by an engine generator is supplied to the electric motor via a converter and an inverter, and an electric power accumulator such as a battery is arranged in parallel to the inverter in a line for supplying the electric power to the electric motor as disclosed in, for example, Patent Document 1 and Patent Document 2.
According to the techniques disclosed in Patent Documents 1 and 2, surplus electric power is stored in the electric power accumulator when the electric power required by the electric motor is small. Therefore, energy efficiency can become high. When the electric power required by the electric motor is greater, the electric power can be supplied to the electric generator from both the engine generator and the electric power accumulator. There is an advantage that the engine generator can be downsized.    PATENT DOCUMENT 1: Japanese Laid-Open Patent Application No. 11-217193    PATENT DOCUMENT 2: Japanese Laid-Open Patent Application No. 11-285165
With the techniques of Patent Documents 1 and 2, a load applied to the engine generator varies in proportion to the electric power necessary for the electric motor. Therefore, if the electric power necessary for the electric motor varies, the activated state of the engine generator also varies. Therefore, it is difficult to optimally maintain the operating state of the engine generator. Said differently, it is difficult to drive the engine generator while maintaining good fuel consumption.    PATENT DOCUMENT 1: Japanese Laid-Open Patent Application No. 11-217193    PATENT DOCUMENT 2: Japanese Laid-Open Patent Application No. 11-285165